1. Field of the Invention
The present invention relates to a flat color CRT, and more particularly, to a flat color CRT (Cathode Ray Tube), in which a flat panel structure is improved, for reducing breakage in a furnace during heat treatment and a weight thereof, to provide a flat color CRT having a weight lighter than CRTs of the same kind, a lower cost, and a shorter tube axis.
2. Background of the Related Art
FIG. 1 illustrates a section a related art color CRT schematically, provided with a panel 1, front glass, welded to a funnel 2, a rear glass, a fluorescent film on an inside surface of the panel 1 for emitting a light, an electron gun which is a source of electron beams 11 for emitting the fluorescent film, a shadow mask 3 for selecting a color so that a desired fluorescent film emits a light, and a main frame 5 for supporting the shadow mask 3.
There are springs 6 for fastening the main frame 5 having the shadow mask 3 fitted thereto to the panel, and an inner shield 7 fixed to the main frame 5 for shielding the CRT from an influence of an external geomagnetism, both of which are enclosed under a high vacuum.
The operation principle of the color CRT in FIG. 1 will be explained. The electron beams 11 emitted from the electron gun built in the funnel 2 are landed on the fluorescent film surface formed on an inside surface of the panel 1 by an anodic voltage applied to the CRT, when the electron beams are deflected in an up, down, left, or right direction, to form a picture.
Since the CRT is at a high vacuum, susceptible to implosion by an external impact, the panel 1 is designed to sustain the atmospheric pressure. Also, the panel 1 is strapped with a reinforcing band 12 at an outer surface of a skirt, for spreading stress to the CRT under the high vacuum, to secure an anti-impact performance.
The related art CRT is provided with the panel 1 and the funnel 2, with the electron gun inserted in a neck part of the funnel 2, which are sealed by evacuation. Under the high vacuum, a substantial tensile, or compression force is exerted on the panel 1 and the funnel 2, to cause an excessive tensile stress at a particular position of a screen of the panel 1.
Currently, it is a trend that the panel 1 is fabricated larger and flatter. FIGS. 2A and 2B respectively illustrate a form of the panel having curves at inside/outside surfaces thereof, and having almost no curve at an outside surface thereof, with a thicker, and heavier panel to cost higher and unfavorable as components, such as the panel, become larger.
FIG. 3 illustrates a flat type panel having no curvature at an outer surface thereof on the left, and a no flat type panel having curvatures at inside and outside surfaces thereof on the right, wherefrom it can be known that the flat type panel has a distance OMH from a molded match line to a seal edge line greater than the same of the no flat type on the right. Thus, the greater overall thickness of the related art flat type panel causes the panel to exceed a critical stress due to a difference of thermal expansion between inside and outside surfaces thereof coming from thermal conduction in a furnace.
Accordingly, the present invention is directed to a flat color CRT that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a flat color CRT, in which a structure of a panel is improved for reducing a ratio of damage of the color CRT in a furnace, and providing a lighter color CRT.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the color CRT having a rectangular panel with an outer surface with a radius of curvature greater than 30,000 mm, an inner surface with a fixed curvature, and a skirt extended substantially perpendicular to the inner and outer surfaces, and a funnel connected to a skirt seal edge part of the panel, to meet conditions of 0.18xe2x89xa6OAH/(USD/2)xe2x89xa60.29, where USD denotes a diagonal effective screen size of the panel, OAH denotes a distance from a center of an outer surface to an extension plane of a skirt seal edge part, OMH denotes a distance from an outer surface molded match line of the panel to the skirt seal edge part, and OSH denotes a distance from the outer surface molded match line of the panel to a skirt brake line, thereby reducing a panel weight compared to the same size of tube for the same effective screen size, that reduces weights of components, resulting to reduce a flat CRT weight in overall, and reduces thermal breakage in a furnace, by adjusting correlations of OAH, OMH, and OSH of an outer surface of a panel.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.